This invention relates to a canister purge solenoid valve. More especially, the invention relates to an improvement for reducing wear and operating noise in such a valve.
A canister purge solenoid valve is a device that is used in certain evaporative emission control systems of automotive vehicles. Its purpose is to control the flow of fuel vapors from a collection canister, commonly called a carbon canister, to the engine intake manifold. The flow is controlled by means of a pulse width modulated signal that is applied to the valve's solenoid from the engine computer. This in turn produces a corresponding modulation of the valve so that the average open time for the valve during each cycle of the modulating signal is similarly modulated.
Evaporative emission standards for automotive vehicles are established by government regulations. Due to changes in applicable standards, evaporative emission systems are required to remove increased amounts of fuel vapors from carbon canisters. Accordingly, it has been necessary to increase the size of the canister purge solenoid valve. Two undesired results of the solenoid valve enlargement are an increase in operating noise level and increased wear on the solenoid's plunger (armature).
The present invention relates to a new and unique construction that is effective to reduce both the operating noise level and the armature wear. Briefly, the elastomeric valve head that opens and closes against the valve seat as the armature is reciprocated, is configured to form one travel stop for the armature during retraction, and an elastomeric member is disposed between the opposite end of the armature and the stator to form a second travel stop. The two travel stops are arranged such that the first travel stop is effective upon armature retraction to begin absorbing the armature momentum just slightly before the second armature stop. The result is a significant reduction in operating noise level and improved durability for the second travel stop.
The foregoing, along with additional features, advantages, and benefits of the invention, will be seen in the ensuing description and claims, which should be considered with the accompanying drawings. The drawings disclose a preferred embodiment of the invention according to the best mode contemplated at the present time in carrying out the invention.